The invention relates to a motor pump unit for a high-pressure cleaning apparatus having a liquid-cooled electric motor and a pump, wherein the electric motor has a motor housing that is surrounded by a cylindrical shell shaped cooling housing with an annular space having an annular space inlet and an annular space outlet formed therebetween, and wherein the pump has a suction inlet connected to the annular space outlet for drawing in liquid and a pressure outlet for discharging liquid, and wherein the liquid to be transported by the pump can be supplied to the annular space inlet and wherein the cooling housing, on its inside, comprises at least one flow guide rib for guiding the liquid within the annular space.
Motor pump units of this type are known from DE 10 2007 009 394 A1. They are used in high-pressure cleaning apparatuses in which a liquid, preferably water, can be pressurized and then discharged via the pressure outlet. The pressure outlet can have connected to it a high-pressure hose with, for example, a spray lance at its free end. This provides the possibility of directing a high-pressure liquid jet towards an object in order, for example, to clean the object.
The pump is driven by means of an electric motor which is cooled by the liquid that is supplied to the pump. To this end, the motor housing is surrounded by a cylindrical shell shaped cooling housing, wherein an annular space is formed between the motor housing and the cooling housing that can be supplied, via an annular space inlet, with liquid to be transported by the pump. The liquid can flow through the annular space and reach the suction inlet of the pump by way of the annular space outlet, so that it can then be pressurized. Flow guide elements in the form of flow guide ribs which are arranged on the inside of the cooling housing guide the liquid through the annular space. In the motor pump unit as described in DE 10 2007 009 394 A1, the flow guide ribs are configured as supporting ribs by means of which the cooling housing is supported on the motor housing.
In many instances, the pump is connected to the public water supply network. As a result, the delivery pressure of several bars, for example 5 to 10 bar, that exists within the water supply network also exists within the annular space. The operability of the motor pump unit requires the annular space to be reliably sealed; in particular it is to be ensured that the motor housing is also impermeable to water on a long-term basis.